The present invention relates to electrical connectors and more particularly to connectors for coaxial cables with a corrugated outer conductor.
Various connectors for coaxial cables with a corrugated outer conductor are described in the literature. Some of these are specifically designed for cables with a helically wound corrugated outer conductor, in which case the helical outer conductor for instance can be utilized to screw the connector onto the cable. The present invention is however intended for corrugated outer conductors which are not helically wound.
Connectors for coaxial cables utilized in connection with high frequency transmission must obtain and maintain an optimal and highly reliable electrical connection between the outer conductor of the cable and the corresponding part of the connector in order to avoid intermodulation problems. Various prior art connectors address this particular problem.
U.S. Pat. No. 5,518,420 (Spinner GmbH) discloses a coaxial cable connector where a suitably prepared end of the outer conductor of a coaxial cable after proper insertion of the cable in the connector is clamped between an end part of the front portion or xe2x80x9cmain bodyxe2x80x9d of the connector and a clamp bushing, where either said end part or said clamp bushing can be provided with beads, which beads due to the clamping force between said end part and said clamp bushing during mounting of the connector on the cable are pressed into the relatively soft material of the outer conductor thus contributing to a more permanently reliable contact between the outer conductor and the front portion of the connector. Somewhat similar connectors are also disclosed in U.S. Pat. Nos. 5,595,502 and 5,795,188 (Andrew Corporation), although these do not contain beads.
It is the object of the present invention to provide a connector for a coaxial cable with a corrugated outer conductor and a hollow inner conductor (which may also be corrugated), which connector facilitates reliable handling hereof during mounting on a coaxial cable with the aim to secure said optimal and reliable electrical connection not only during mounting of the connector on the cable but also during the whole operational life of the connector.
Accordingly, it is an object of the present invention to provide a connector for a coaxial cable with a corrugated outer conductor and a hollow inner conductor which connector makes it possible in an easy and reliable manner to ascertain that the correct final placement of the connector on the cable has in fact been obtained.
It is a further object of the present invention to provide a connector for a coaxial cable with a corrugated outer conductor and a hollow inner conductor which connector consists of a minimum of constituting parts and where the construction of the connector is such that the dimensions of the connector can be kept at a minimum, thus saving material during manufacture and saving space and weight, which is advantageous during transport and shipment of connectors.
These and other objects are achieved with a connector according to the characterizing clause of the independent claim. Various embodiments of the connector according to the invention are set forth in the dependent claims.
According to the present invention, there is thus provided a connector for a coaxial cable with a corrugated outer conductor and a hollow inner conductor, where said connector comprises the following components: a tubular main body to be placed coaxially on said cable and electrically connected to the outer conductor of the coaxial cable, said main body containing the center terminal of the connector, where a first end of said main body facing the coaxial cable consists of a tubular extension of a first diameter; a tubular bushing to be connected coaxially to said main body and which can be displaced longitudinally a certain, limited distance relative to said main body, for instance by screwing said bushing onto said main body with the aid of threads suitably positioned on an outer surface of said main body and on a corresponding inner surface of said bushing; a tubular, resilient bushing placed around said tubular extension of the main body, so that said tubular extension can slide longitudinally within said resilient bushing; a rigid ring member placed coaxially around said resilient bushing in engagement partly herewith and partly with said bushing and forming a circular gap between said resilient bushing and said rigid ring member, the width of said gap being suitably dimensioned to be able to contain an end portion of the outer conductor of the coaxial cable, and where said width of said gap is being brought to decrease when said resilient bushing is being displaced longitudinally over said tubular extension of the main body in the direction towards that end of the connector facing away from the coaxial cable, so that said end portion of the outer conductor of the coaxial cable thereby is being retained firmly within said gap and such that a reliable electrical contact is herewith established between said outer conductor and said main body; a center terminal of the connector attached to said main body via an intermediate tubular insulator and positioned coaxially with said other parts of the connector and with the coaxial cable, said center terminal is introduced within the interior of said hollow inner conductor of the coaxial cable and thereby establishes a reliable electrical contact between the center terminal and the inner conductor.
According to the present invention, said resilient bushing is at the end thereof facing the coaxial cable provided with a radially outwardly extending circumferential protrusion, the outer diameter of which is slightly larger than the minimum of the inner diameter of the corrugated outer conductor of the coaxial cable. As will be further described hereinbelow, when the connector is mounted on the end of the suitably prepared cable, the end of said outer conductor will pass over said protrusion, which is possible due to the resilient construction of said resilient bushing, which passing will produce an audible xe2x80x9cclickxe2x80x9d and/or a vibration in the connector, which can be perceived by the person fitting the connector on the end of the cable. This xe2x80x9cclickxe2x80x9d or vibration will thus indicate to the person fitting the connector that this has been properly positioned on the end of the cable. The inner diameter of said resilient bushing (i.e. the diameter of the hollow inner part hereof) varies so that said inner diameter is less at the end of said resilient bushing comprising said protrusion than at the other end hereof, this other end having an inner diameter substantially equal to the outer diameter of said tubular extension of the main body. When hereafter said main body and said bushing as a final step of the mounting of the connector on the cable is displaced relative to each other for instance by screwing said bushing onto said main body, said tubular extension of the main body will be displaced longitudinally in said resilient bushing, so that when during this displacement said inner diameter of the resilient bushing becomes less than said outer diameter of the tubular extension of the main body, the end hereof provided with said protrusion is being pressed radially outward towards the rigid ring member and thereby establishing electrical contact between the outer conductor and the main body as well as a firm and reliable mechanical attachment therebetween as described previously.
Thus according to a first aspect of the invention, there is provided auditory or tactile means for ascertaining the correct insertion of the cable in the connector.
According to a second aspect of the invention, there is furthermore provided a connector which establishes reliable electrical connections between said center terminal and said inner conductor and between said main body and said outer conductor respectively by carrying out the following series of steps: inserting the suitably prepared end of the coaxial cable in the connector to a point where said xe2x80x9cclickxe2x80x9d and/or vibration is perceived; displacing the main body and the bushing of the connector longitudinally relative to one another for instance by screwing the bushing onto the main body until a stop position is reached, whereby said contacts are established.